From Wikipedia, the free encyclopedia
Geological formation
The Gravel Point Formation is a
geologic formation in western
Michigan . It preserves
fossils dating back to the middle
Devonian
period and correlates with the
Long Lake Limestone and
Alpena Limestone .
[1]
Description
The
Michigan Basin was a shallow marine shelf during the middle
Devonian , located between 30º South and 20º North latitude in central
Laurasia . According to stratigraphic and paleontological examination, the sediments of the Gravel Point Formation were deposited in a shallow
lagoonal reef environment.
[1]
Fossil content
Vertebrates
Acanthodians
Bony fish
Placoderms
Invertebrates
Several species of
ostracods , an unidentified
arthropod 'hook',
crinoid columnals and several species of
polychaetes and
scolecodonts are known from the formation.
[1]
Brachiopods
Brachiopods of the Gravel Point Formation
Genus
Species
Presence
Material
Notes
Images
Atrypa
A. corrugata
[1]
Douvillina
D. sp.
Lower part of the formation.
[3]
2 specimens.
[3]
Heteralosia
H. sp. B
2 pedicle valves.
[3]
Leptalosia
L. radicans
[3]
Also found in the
Norway Point ,
Alpena ,
Four Mile Dam ,
Genshaw ,
Arkona and
Hungry Hollow formations.
Longispina
L. emmetensis
[3]
Also found in the
Alpena Limestone and
Four Mile Dam Formation .
Mucrospirifer
M. latus
[1]
A
spiriferid .
M. sp.
[1]
A
spiriferid .
Oligorhachis
O. oligorhachis
[3]
Also found in the
Four Mile Dam Formation .
Orthopleura
O. sp. A
"Large Atrypa zone".
[3]
One specimen (U.S.N.M. no. 124258).
[3]
O. sp. B
"Upper Blue shale".
[3]
One specimen (U.S.N.M. no. 124280).
[3]
Pentamerella
P. aftonensis
Gorbut Member.
[3]
P. alpenensis
[3]
Also found in the
Alpena Limestone and
Four Mile Dam Formation .
P. sp. D
A small collection of large shells (the largest being 38 millimeters).
[3]
Pholidostrophia
P. geniculata
[3]
Also found in the
Alpena ,
Widder and
Hungry Hollow formations.
Pseudoatrypa
P. keslingi
[1]
Schuchertella
S. anomala
[3]
Possibly also found in the
Four Mile Dam Formation .
Strophodonta
S. costata
[1]
A
strophomenid .
S. cf. S. erotica
[1]
A
strophomenid .
S. erratica
[3]
Also found in the
Alpena Limestone and
Four Mile Dam Formation .
S. fissicosta
Upper part of the formation.
[3]
Also found in the
Four Mile Dam Formation .
S. nanus
[3]
Also found in the
Alpena Limestone and
Four Mile Dam Formation .
S. titan titan
[3]
Also known from the
Alpena Limestone .
Truncalosia
T. gibbosa
[3]
Also found in the
Alpena ,
Genshaw ,
Norway Point ,
Petoskey and
Potter Farm formations, the
Arkona Shale and the
Hamilton Group .
Tylothyris
T. subvaricosa
[4]
Also found in the
Cedar Valley ,
Milwaukee ,
Mineola ,
Bell ,
Rockport Quarry ,
Ferron Point ,
Genshaw ,
Alpena ,
Norway Point and
Potter Farm formations.
Bryozoans
Cnidarians
Sponges
Tentaculitans
Trilobites
Color key
Notes Uncertain or tentative taxa are in small text ; crossed out taxa are discredited.
Flora
Algal colonies are known from the formation.
[1]
Acritarchs
Plants
See also
References
^
a
b
c
d
e
f
g
h
i
j
k
l
m
n
o
p
q
r Mohan, Joseph (November 2013).
"A Paleoenvironmental Analysis of the Middle Devonian Gravel Point Formation, Western Michigan" . The Professional Geologist . 50 (6): 12–16.
^
a
b
c
d
e
f Stack, Jack; Sallan, Lauren (2018-09-20).
"An examination of the Devonian fishes of Michigan" . PeerJ . 6 (2): e5636.
doi :
10.7717/peerj.5636 .
PMC
6151260 .
PMID
30258725 .
S2CID
52843222 .
^
a
b
c
d
e
f
g
h
i
j
k
l
m
n
o
p
q
r
s
t Imbrie, John (1959).
"Brachiopods of the Traverse group (Devonian) of Michigan. Part 1, Dalmanellacea, Pentameracea, Strophomenacea, Orthotetacea, Chonetacea, and Productacea. Bulletin of the AMNH ; v. 116, article 4" .
hdl :
2246/1258 .
^ Rogers, Frederick S.; Pitrat, Charles W. (May 1987).
"Distribution of Tylothyris (Brachiopoda) and its occurrence in the Traverse Group (Middle Devonian) of Michigan" . Journal of Paleontology . 61 (3): 494–507.
doi :
10.1017/S0022336000028651 .
ISSN
0022-3360 .
S2CID
130922140 .
^
a
b
c
d
e
f Watkins, J. Lloyd (1959).
"Middle Devonian Auloporid Corals from the Traverse Group of Michigan" . Journal of Paleontology . 33 (5): 793–808.
ISSN
0022-3360 .
JSTOR
1300915 .
^
a
b
c
d
e
f
g Stumm, Erwin (1953).
"Trilobites of the Devonian Traverse Group of Michigan" (PDF) . University of Michigan Press - Museum of Paleontology .